Azure Load Balancer operates at the 4th OSI layer which acts as a single point of contact for clients.
Load Balancer distributes inbound flows that arrive at the load balancer's front end to backend pool instances. These flows are according to configured load balancing rules and health probes. The backend pool instances can be Azure Virtual Machines or instances in a virtual machine scale set.
Azure has public and also private/internal load balancer.
Load balancer provides low latency and high throughput and scales up to millions of flows for all TCP and UDP applications.
Using an Azure load balancer, you can balance the internal and external traffic to virtual machines, increase the availability of the distributing resources, use port forwarding, etc.